1. Field of the Invention:
The invention relates in general to gas-insulated transmission lines and in particular to gas-insulated transmission lines having a corrugated outer conductor and a particle trap contact means suitable for electrical continuity between the particle trap and the corrugated outer conductor.
2. Description of the Prior Art
Compressed gas-insulated transmission lines typically comprise a hollow, cylindrical outer sheath, an inner conductor disposed within, but spaced apart from, the outer sheath, a plurality of insulating spacers which support the conductor in the sheath, and a compressed gas such as sulphur hexafluoride or the like in the sheath to electrically insulate the inner conductor from the sheath or outer conductor. One problem occurring in the use of gas-insulated transmission lines concerns the mobile conducting or semiconducting particle. These particles can cause problems in that they may lower the dielectric strength of the insulating gas and may initiate flashover and breakdown of the gas as they travel between the outer sheath and the inner conductor. Trump, in U.S. Pat. No. 3,515,939, disclosed the means for deactivating and eliminating the deleterious effects of such conducting particles. In that patent, there is described the use of electrodes placed within the outer sheath to create low field regions which trap and deactivate the particles. The low field regions are created by keeping the particle trap electrode at the same potential as that of the outer sheath or outer conductor by means of a particle trap to sheath contact.
A recent development proposes to use corrugated aluminum for the outer conductor instead of the smooth aluminum cylindrical outer sheath. With such a corrugated outer conductor, standard particle trap to sheath contacts are not suitable to keep the particle trap in contact with the corrugated outer conductor and thereby at the same electrical potential. This is because of the large variation between the inside diameter of the sheath and the outside diameter of the particle trap assembly due to the peaks and valleys of the sheath corrugations and because motion occurs between the inner conductor/insulating means/particle trap assembly and the outer corrugated conductor of a gas-insulated transmission line both when the transmission line is first assembled at the factory and while it is in service due to temperature differences between the outer and the inner conductors. Accordingly, it would be desirable to maintain a firm electrical contact between a corrugated outer conductor and a particle trap regardless of the axial position of the particle trap.